In ink-jet printing methods, droplets of ink are directly projected onto a recording medium from very fine nozzles and allowed to adhere to the recording medium to form characters or images. The ink-jet printing methods have been rapidly spread because of their various advantages such as easiness of full coloration, low costs, capability of using a plain paper as the recording medium, non-contact with printed images or characters, etc.
However, in the ink-jet printing methods, since a solution or dispersion of a colorant containing a large amount of a solvent is ejected as an ink for printing on a recording medium such as papers, there tends to occur such a problem that especially when using a water-based ink as the printing ink, the ink is penetrated and spread along fibers in the papers to thereby cause deterioration in clarity of images printed, etc., as compared to the other printing methods.
To solve the above problems, there has been proposed the method in which a recording medium such as papers is previously subjected to the treatment for insolubilizing a colorant applied thereonto, etc.
For example, Patent Document 1 discloses a method for forming color images in which after applying a colorless liquid composition containing a silicone compound and a cationic compound onto a recording medium, an ink containing an anionic group-containing dye, etc., is applied and attached onto the recording medium in an ink-jetting manner, for the purpose of improving an optical density of printed images on plain papers, ink bleeding, a color reproducibility or the like.
Patent Document 2 discloses an oil-based ink for stamp pads which contains a poly(N-acylalkylene imine)-modified silicone, a colorant and a solvent, for the purpose of improving a repellency and adhesion of the ink.
In addition, Patent Document 3 discloses an ink-jet printing method in which after applying a treating solution containing a treating material selected from a block or graft copolymer produced from a dialkyl siloxane and a polar hydrophilic monomer, an organopolysiloxane copolymer, etc., onto a recording medium, an ink composition containing water and a colorant is loaded in an ink-jet printer, and then ink droplets are ejected onto the recording medium to obtain printed images thereon.    Patent Document 1: JP 8-142500A    Patent Document 2: JP 2004-83693A    Patent Document 3: U.S. Pat. No. 6,270,214